Remote control system



Filed Dec. 23. 1931 INVENTOR H. B ARN 01. D

A TTORNEV Patented Dec. 13, 193 2 UNITED STATES PATENT" OF -1C5? HENRY B. ARNOLD, on NEW YoRx, N. Y., ASSIGNOR TO BEL TELEPHONE ARoRAToRIEs,

INCORPORATED, or NEW YoRx, N. Y., A co PoRATIoN or Ew yo x REMOTE ooN'rRonsvsrm/r Application filed December 23, 1931. Serial No. 582,700.

This invention relates to remote control systems and'particularly to systems for remotely controlling the operation of a radio receiving station employed for monitoring 5 the operation of a radio broadcast transmitter.

- i In the copending application of vGr. D. Gillett, Serial No. 460,246 of June 10, 1930, there is disclosed and claimed a system for monitoring the operation of radio broadcast transmitters so that one or more transmitters can be operated on the same wave length. In this system there is located ata point in the operating field of two. such. broadcast transmitters, a radio receiving station which is connected by a wire line to one of the transmitters. The operationof this transmitter is controlled by observing the signals transmitted from the receiver station over the wire line.

I An. object of this invention is to remotely control such a receiver station over the lines used for transmitting the signals.

7 Since the proper regulation of the transmitter depends upon the continuing operation of the receiving equipment, it has been found desirable to employ at the receiver station a stand-by receiver and associated apparatus. As pointed out in the Gillett application referred to above, it is highly advantageous to supply to the receiver along with the signal an audio frequency tone.

Consequently, the control circuit is required to perform the following operations:

1. Turn on and off either of the two radio receivers and their associated tone generators.

2. Turn on and off the tone generator of the receiver in operation. 7

3. Provide different conditions of gain for each receiver. V

invention, control is effected by means of two three-position polarized relays, one of which is connected between each side of the signal transmission line and ground. One relay controls the energization of the receivers and tone generators and is arranged so that when it is in the neutral position both sets are OK and when operated in one direction turns on one set, and when operated in the other mitter 5. In a specific preferred embodlment of th1s direction turns on the other set. The second relay provides three positions, in one of which positions the 'tone generator. is operated. r .The relays are operated by two threeposition keys located at the distant end of the transmission line. Each of these keys is so connected that in its neutral position no current is applied to: the 1ine, while in oneextreme position, current is caused to flow in 6 "one direction through the line andin the other. extreme position current is caused to flowin the opposite direction. Inaddition there are provided at the'control point means for indicating the circuit conditionfat the re--.

ceiver station. Filters are used at eachline terminal for separating the control and signal currents. V

"This invention can be more readily understood byreference to the following detailed description in connection with the drawing inwhichz H Fig. 1 is a schematic drawing of the general lay-out of one embodiment of-theinvention; and 1 r Fig. 2 isa schematic drawingshowing in (Iistali control circuits ofthe systemshown in 1g. V v a 1 Referring to Fig. 1, there are shown two radio transmitters 5 and G'Which are arranged to operate at the same carrier frequency for transmitting the same program. Intermediate-the two transmitters there is located a receiver station 7. This station is preferablyso positionedthat the amplitude 35 of the waves received from the transmitters 5 and 6 in the antenna 8 are substantially equal. The receiver stationis connected by a wire line 9 Which'terminates at the trans v 1 i At the receiver station 7 there arelocated two radio receivers 10 and 11 both having their inputs connected to the loop'antenna 8 line 9 through the condensers 17.

na 8 are detected and, transmitted over the wire line "9 -to-give a response in theloud speaker 16. The control circuit can also be operated to, cause the receiver connected at any time to operate a-t a desired gain with or without the associated audio frequency os- Qci-l'lator supplying :an audible frequency tone .thereto...

Asisdescribeid in detail in the acopending application of D. E. Gillett, Serial No. 460,- Qritfiinefenredto above,=this system-can be oper- .:'ated tozhold the two transmitters 5 :and "-6 in substantial isochronism, When the audio frequency osci llator at the receiver station is ppenated, the carrier waves greceived in the lzan-tenna "8rare modulated in the radio frewquencyk-azmplifienof the :receiver '10 or 11 by the .zaudio frequency tone and the resultant wvarve implifiedjand detected and transmitted over, the wire line 9 to give an. audible indication 1111 theiloud speaking receiver- 16. If. the 'frequencywof one of the transmitters 5 or; 6' ;5Vfl1ileS to throw the '.two transmitters out of isochronism, this audio frequency output waue:will go: through a fading cycle the f requency of which is the actual differencefin the frequencies of the carrier waves in the two transmitters. By observing the frequency oft-his fading cycle as :auidibly indicated :in the receizwer i=6, the operator is able to adjust the frequency of thecar-rier wave zofg-thewtransmitter 5 so as to holdthe two waves to any desired degree of isochronism. When the receiver 10V or 11 is operated withoutfithe audio frequency oscillator, the detected r-si-gnal or program will :go through a similar fading cycle and permit monitoring .the operation of the transmitters in the same way; As discussed in the Gillett application,

the 11SBi0f theaud ible tone from'the oscillator makes possi-ble the adjustment of the transmitters when they are 7 operating to transmit .a carrier without a modulating signal or program and also to give an indication which is ..i=ndependent of :any musical rhythm or beat in the program being transmitted. However, it .is'ofte-{n .z esirable "tojoperatethereceiver with- ."outthe oscillator, forexample, to get a direct indication of the quality of the receivedrzprogram at the monitoring point.

F ig. 2 .showsschematically the details of the control circuit by which the apparatus at the receiver station 7 is controlled from the transmitter station 5 over the wire line 9. For the purposes of simplification, the radio receivers 10 and 11, and oscillators113. and 1.4

are shown only as boxes with a single tube in each. The receivers may be of any well known type, for example, each may comprise a radio frequency amplifierin which thereceived waves are amplified and modulated by the audio frequency tone fromthe oscillator,

.a detector and an audio frequency amplifier.

The single tubes 20 and 21 shown in the receiv ers 10 and 11 are of the screen grip type and comprise the first of two of the radio frequency-amplifiers. They are shown for the purpose of. indicating how the power supply connections are made to the radio receivers since the control is effected through the power supply connections. Similarly, each of the oscillators 13 and 14: is indicated merely as a box with a tube 23 and '24 respectively indicated "in each; The tubes are shown merely for the purpose 'of'indicating how the power supply connections are "made and the details of the oscillator circuits are omitted.

Battery 25 supplies cathode heating currentto the tubes of the receivers and 'oscil- .l'ators. -Battery 26 supplies space current-- to the tubes of the oscillators. {Battery :27

supplies space current to the radiofreceivers lO-and 11-. V V

Theoutput circuit of the oscillator. 13 com prisesa blocking condenser29 in series with a tubes of the resistance '30 and :a potentiometer .81 connect ed between the plate and grounded cathode, .A portion oflthepotential drop across the potentiometer 31 is fedacross the tuned loop circuit. .In this way the audio frequency tone from the oscillator is impressed on the grid-cathode circuit of the first tube of the radio receiver 10 along with the radio-wave received in the loop 8.. .Tlie' choke @0'11'32 is provided inthe link circuit of the oscillator tube 23 to separate'the direct current com- 'ponent of the space current from thegenerated alternating current.

'larlycondenser- 33, resistance 34 and choke coil 35 are provided in the plate circuit of the tube 2410f the oscillator 14-. The

loop circuit 8 including the potentiometer 31 is common 'to .thecircuit of'the two oscillators and receivers: v r

The amplitude of the audio tone supplied by the oscillator 13 or 14 is controlled by the potentiometer 315 Thisis preferably set sothat audio tone amplitude is such asto overmodulate the receivedcarrier waves, the modulation taking place in the radio frequency amplifier of the radio receiver. After the resultant waves are detected in'the radio receiver detector the low frequency beat note representing the frequency difference between the two .c arriers'will appear superimposed'on theaudio'tone'causin g arise and fall 7 in. the intensity thereof with easily recognizable minimums. Whilethe system is normally operated with theaudio tone modulation asgj ust described itsometimes may be desirable to operate it with :normal reception, for example, to check the actual reception conditions. For this purpose there is provided a control for rendering the audio oscillators inoperative and inceasing the screen grid bias to give an increased gain as will be described later.

The control of the receivers and oscillators is effected by means of'two three-position polarized relays and 50. Belay 40 is connected between the lower Wire of the transmission line 9 and ground. Relay 50 is connected between the upper wire of the transmission line 9 and ground. The condenser 12 prevents the direct current for operating the relays 40 and 50 from reaching the recievers 10 and 11.

Relay 40 controls the turning onand off of the radio receivers 10 and 11 and their associated oscillators 13 and 14 respectively.

When the relay 40 is in the unoperated position, the cathode heating circuits of the receiver and oscillators and the screen grid polarizing circuitsof the receivers are open. The operation of the relay closes these circuits for theselected receiver. 1 I The operation of the relay in such a direction as to close the left-hand contacts of armatures 41 and 42 closes the cathode heating circuit of the receiver 10 and the oscillator 13 from ground, through battery 25, armature of relay 41, and in parallel through cathode of the oscillator tube23 to ground and re sistance 36 and the receiver cathode heating circuit to ground. At the same time, the circuits for the screen grids of the tubes of the radio receiver 10 are closed from the screen,

through the manual gain control. potentiometer 37, armature 42 of relay 40, connection 38, resistances 43 and 44, lower half of resistance 48, battery 27 to round. The resistances 43 and44 provide means for remotely controlling the gain of the receivers as is described below in connection with the description of the operation of relay 50.

Similarly, when the relay 40 is operated to its right-hand position, the cathode heating circuit of the radio receiver. 11 and the oscillator 14 and the screen grid circuit of the radio receiver 11 are closed through the righthand contacts of the armatures 41 and 42, the resistances 39, 49 and 54 of the receiver 11 and the oscillator 14 set, these resistances corresponding to the resistances 36, 37 and 48 tions these platecircuits are opened, and the potential of the screen grids of the receiver tubes increased. The two operated positions correspond to different degrees of increase of thescreengrid potential and hence different gains for the receivers. .They are provided to -meet different operating conditions; for example, one may'provide the. proper gain for operation under day transmission conditions and the other for night.

'.When the relay 50 is in its neutral posi tion (as shown in the drawing), the plate current circuits of the oscillators 13 and 14 are completed from ground, through battery 26, armature'52 of relay 50, and choke coil 32 to the plate of the'oscillator' tube 23 or choke coil 35 tothe plate of the oscillator tube 24. As a result when the relay 40 is operated to complete the cathode heating circuit of either the tube 23 or 24, that tubewill 11 by meansof the connection throughthe armature 51 and its left-hand contact. This causes the receivers to operate at an intermediate gain position. When the relay 50 is operated to its right-hand position, both of the resistances 43 and 44 are shunted out of the screen grid circuit so that the receivers operate at a conditionof high gain.

i The relays 40 and 50 arecontroll'ed by 9, the control being effected by means of the control circuit 18 located 'atthe station of the transmitter 5. Keys 45 and 55 control the supplying of direct current to the lower r and upper wires of the line 9 to control the relays 40 and '50 respectively.

When the key .45 is operated to its upper 7 position battery 46 is connected to supply positive current 'to the lower wire of the line 9 causing the relay 40 to operate, foreX- ample, to its left-hand position to energize the receiver 10. In a similar manner, when the key 45 is operated in its lower position, the battery 47 is connected to supply negative current to the lower wire of the line 9 to operate the relay 40 to its right-hand position so as to energize the receiver 11.

means of current supplied over the wire line The batteries 56 and 57 associated with the key 55 permit a similar operation of the relay50 by actuating the key 55. When the key 55 is operated in its upper position, the

battery 56 is connected to supply positive current in the upper wire of the line 9 and causes the relay 50 to operate to its left-hand position to render the oscillator 13 or 14 inoperative and cause the receiver to opcrate at an intermediate gain. Similarly,

when the key 55 is operated to its lower position, battery 57 is connected to supply our- .rent of'negative polarity to the upper wire of the line Qcausing the relay 50 to'operate to itsright handposition rendering the :os

cillator 13 or 14 inoperative and causing the receiver to operate. at itsmaximum gain.

Relays 70 and 80 and their associated lamps.

73,74,7'5-and '83, 84, '85 are provided to give an indication of the operative con dition'of the controlcircuit. Relay 70is connected in series with the key 45., lwer wire of the line 9 and relay l0. Relay-"80 is similarly connected in series in the operating circuit .for the relay 50. Thus, when the key or 755' is operated, the respective relay or 1 .will operate in the same manner as the relays "40 and 50 of the controlled station completing a circuit for lighting the respective indicatm lamp 73, 74, 75, s3, 84 or 85. a v The lighting current for these lamps is supplied from an alternating current source such as an ordinary lighting circuit through the transformer 86. o

" The auxiliary contacts 76 and 7 7 are provided on the key 45 so that indicating lamps 83, "Stand 85 will light only: when the key '45 is in one of its extreme positions to rendera radio-receiveranditsasso'ciated oscillator flogperativel I What is claimed is; I

-'-' '1'; In combination in a radio system, a "re- 'celving antenna, a signal transmissmn line,

:a pair of normally deenerg-ized radio'receivers havmg-thelr inputs connected to sa d antenna and their outputs connected in parallel to said .line, vrelay means responsive to current prone polarity for energizing one-of saidradro receivers and responsiveto current Pof theoppo'site polarity for :energ'zing the other of "said radio 1receivers',$an audio frequency oscillator connected to supply waves to each "of sa1d radlo receivers for modulating the received wave. other relay n1eans-respons1ve 'tovcurrent of one polarity for causing operating each of said relay means over said signal transmission line.

2i A combination according to ,th e next prebeding claim in which said signal transmission'. line is a two-wire line and each of said relay meansfls' connected between one of said wires and ground; r

, 3.' Elna system for 'simultaneously operating a plurality of radio transmitters at the same carrier frequency havlng 'a Inc-mitorin'g receiving station anda wire line connecting said receivingistation with one of said trans- -H1ltt6IS, in combination, two radio receivers located at said monitor-ing'stati'on, anantenna adapted to receive waves from both of the transmitters connectedtothe inputs of both 0f said receivers, an oscillator associated with each' of said receivers for supplying waves for modulatlng the wave recelved thereby,

means opaque to direct current'but capable of transmitting alternating current for connecting the outputs of both of said receivers to said transmissionline, relay means connected r between one wire of said transmission line and ground, said relay means being-responsive to direct current of one polarity for energi'zin-g; one of said radio" receivers and responsive'to direct current ofJthe opposite polarity for energizing the other. of said radio receivers and when in a non-operated position arranged-to deenergize both of said radio receivers, other relay means connected be- 7 tween the other ofsaid wires ofsaidtransmission lineand ground and arranged when. in a non-operated position to render operative that one of the oscillators: associated with that one of the radio receivers then in an operating condition and being responsive to direct current of one polarity for rendering inoperative sa1d oscillator and causing sa1d radio receiver tooperate at an increasedgain i.

and being responsive to direct current of the opposite polarity for. rendering inoperative said oscillator and causing said receiver to operate at a, difierent increased gain, signal responsive means connected to the terminalof sa1d transm1ss1onl1ne at sa1d radlo transmitte'r station, and controlmeansat-saidtransmitterstation for supplying operating current for sa d relay means between each of the Wires of said'transmission line and ground.

4. In combination a two-wire signal transmission line, an antenna, two audion radio receivers having their inputs connected to saidantenna and their outputs connected to 1 one terminal 'ofsaid transmission line, an audion oscillator for supplying waves to each of said radio receivers for modulating the received wave, relay means "having :an operating winding connected between one 'larity for supplying-cathode heating current to the audions of oneof said radio receivers and of the osclllator associated with-said one of sa1d radiorecelvers and responsive tocurrent of the opposite polarity for supplying cathode'heati n g current to the audions' of the other of said radio receivers and ofthe oscillator associated with said other of said radio receivers, said relay'means being ar- 7 ranged so that when 1t is in the unoperated position the cathode'heating current sup-. ply 'to both of said receivers and oscillators is disconnected, other relay means '"having 11; of the wires of said transmission line and -groundand responsive to current of one *poan operating winding connected between the other wire of said transmission line and ground being arranged so that when it is in the unoperated position space current is supplied to both of said oscillators, and being responsive to current of one polarity for interrupting the supply of space current to said oscillators and conditioning said radio receivers to operate it at a predetermined increase in gain and being responsive to an operating current of the'opposite polarity for interrupting the supply of space current to said oscillators and conditioning said radio receivers to operate at a difi'erent predetermined gain, means connected to the other terminal of said signal transmission line for giving an indication of the output of said radio receivers and means also connected to said other terminals of said signal transmission line for supplying operating current between each of the wires of said line and ground for controlling the operation of both of said relay means.

cause said radio receivers to operate at a different predetermined gain, means connected to the other terminal oi said signal transmission line for giving an indication of the output of said radio receivers, and means also connected to said other terminals of operating current between each of the wires of said line and ground for controlling the operation of both ofsaid relay means.

In witness whereof, I hereunto subscribe my name, this 21st day of December, 1931.

HENRY B. ARNOLD.

5. In combination a two-wire signal transmission line, a receiving antenna, two radio receivers each having an audion of the screen grid type and having their inputs connected to said antenna and their outputs connected to one terminal of said transmission line, an audion oscillator for supplying waves to each of said radio receivers for modulating the received wave, a resistance network for controlling the voltage applied to the screen grid of the audion of said radio receivers,

relay means having an operating winding connected between one of the wires of said transmission line and ground and responsive to current of one polarity for supplying cathode heating current to the audions of one of said radio receivers and of the oscillator associated with said one of said radio receivers and for connecting the screen grid of said one of said radio receivers to said resistance network and responsive to current of the opposite polarity for supplying cathode heating current to audions of the other of said radio receivers and of the oscillator associated with said other of said radio receivers and for connecting the screen grid of the audion of said other of said radio receivers to said resistance network, said relay means being so arranged that when it and being arranged so that when it is in the unoperated position space current is supplied to both of said oscillators and being responsive to current of one polarity for interrupting the supply of space current to said ossaid signal transmission line for supplying 

